1. Field of the Invention
The present invention relates to a printing device having a printing mechanism, such as a thermal head, etc.
2. Description of the Background Art
FIG. 20 is a conceptual diagram showing a mechanism 100 of a conventional printing device (a heat transfer printer device). In FIG. 20, 1 denotes a thermal head, 2 denotes an ink sheet coated with thermo-dissolving ink or thermo-sublimating ink for heat transfer recording, 3 denotes printing paper, 4 denotes a platen roller for transferring the sheet of printing paper 3 while pressing the sheets in close contact with each other against the thermal head 1, 5 denotes pinch rollers for transferring the printing paper 3 while gripping the paper, 6 denotes a cutter for cutting the roll-type printing paper 3, and 7 denotes a reflection-type optical sensor for sensing the front end position of the printing paper 3.
FIG. 21 is a conceptual diagram showing the conventional thermal head 1. The effective heating width W1 of the thermal head 1 is shorter than the paper width W2 of the printing paper 3. FIG. 22 is a diagram showing the front side of a printed piece of paper 300 produced in the conventional system.
The conventional printing device operates as described below. Initially, suppose that the cutter 6 has cut the printing paper 3. The pinch rollers 5 transfer the printing paper 3 in the paper-supply direction. In the feed direction in which the printing paper is sent, the direction from the printing paper supplying side to the printed paper discharge side is referred to as a paper-discharge direction and the opposite direction is referred to as the paper-supply direction. The sensor 7 senses the front end 31 of the printing paper 3. The pinch rollers 5 position the front end 31 at the position of the pinch rollers 5 based on the information about the position of the front end 31 sensed by the sensor 7. Next, a desired image 30 is printed. Then, the pinch rollers 5 transfer the printing paper 3 in the paper-discharge direction and position the rear end 32 at the position of the cutter 6 such that a blank 34 is left. Then the cutter 6 cuts the printing paper 3. In the conventional system, the positioning of the printing paper 3 is thus obtained on the basis of the positional information about the front end 31 of the printing paper 3.
The conventional heat transfer printer device has the following problems. Since the effective heating width W1 of the thermal head 1 is shorter than the width W2 of the printing paper 3 as shown in FIG. 21, the printed piece of paper 300 has blanks 35 in its width direction, as shown in FIG. 22. Further, since the conventional heat transfer printer device operates as described above, blanks are left in the feed direction on the printed piece of paper 300, as shown in FIG. 22. More specifically, the printed paper has a gripping blank 33 having the width L from a pinch rollers 5 to the thermal head 1 and a margin blank 34 for preventing the image 30 from being cut.
Further, the positioning of the printing paper 3 is obtained on the basis of the information about the position of the front end 31 and not on the basis of contents on the back side of the printing paper 3. Accordingly, the conventional heat transfer printer cannot be applied to printing that requires that contents on the front side of the printed paper 300 should be positioned in correspondence with contents on the back side, as in the case of picture postcards.